My friend works at a company with unlimited vacation and they pay you $1000 for every full week you take off.
In Sweden you actually get a ~12% higher pay during your vacation.
I think the idea is that you should be able to spend while on vacation... but not really sure.
This was introduced because in the 1960s and 70s a lot of skilled workforce (several %, tens of thousands of people) emigrated to Sweden, in particular to work for Volvo, Saab and other industries. Workers had their full (4 weeks or so) summer vacation and then left for Sweden, where they were offered a house, a car and a relocation package.
This pattern kept repeating for a few years, so to counter the wave of emigration, the after-vacation bonus was introduced.
Some places use this as a benefit to lure employees. For example I worked at a place where I got 75% extra pay on vacation days.
The downside is that getting more than the minimum mandated by law (6 DAYS a year) is not that common. For example, for that place that gave 75% extra, I had I believe 10 (or 12) days a year, and it was actually above industry standard.
Edit: To answer one of the posters below, I believe someone once explained to me, that at least in Mexico, the extra pay is supposedly to make it easier for families to actually go out of town and spend money, so it becomes a factor that helps drive the economy. I.e. if you have vacations but no money, then you won't spend anything and ultimately won't take vacations. This way you get vacations and also have money to spend during those days. At least that's how it's supposed to go.
Paid, paid (paid2) vacations: We’re so serious about you being recharged that we go above and beyond your regular paid vacations; you’ll get an extra $1,000 when you take a week off of work and fully “unplug” (no work, no exceptions!).
Depending on your base pay, I guess it could be around 8-12% for most developers.